Rotary cutter



Sept. 24,1946. A5 FDOR A 2,408,257

fRoTARY GUTTER Filed Feb. '1, 1944 l Fig! v `lNvENToR v v Andrewadar, 30 I r ATTORNEYS Patented Sept. 2K4, 1946 n,

UNITED Y STATES PATENT OFFICE y RoTARY CUTTER y Andrew S. Fodor, South Norwalk, Conn. Application February 1, 1944, Serial No: 520,641

13 olaiis.

This invention relates to rotary cutting tools, and more particularly to means for supporting the cutter elements of such tools.'

An object of the invention is to provide an' improved rotary cutting tool for cutting through a considerable thickness of plate, wherein the cutter elements ofthe tool, which are strongly backed, While readily individually removable for sharpening,V regrinding, etc., are positively held against shifting radially (laterally of the backing) during use of the tool.

This is accomplished by shaping the cutting elements and the backing Vmembers therefor so that one nests into the other. The'arrangement is such that the cutting elements are held in position by conveniently removable screws, yet the mounting does not rely on the screws for supporting the cutters'to prevent lateral movement thereofl A feature ofthe invention is the provision of a nesting engagement between'the cutter and backing member as above set forth which is simple and economical to produce. In the embodiment shown the cutter', which has an elongate shank, is ground so that it can be set in a posi' tion Where it presents a corner of the shank for engagement with the backing member, and the latter is provided with a V-groove Which receives and nests the corner of the cutter shank. The backing member is of heavy construction, having cylindrical inner and outer surfaces so that it Withstands lateral or radial pressures to a considerablevdegree, and this rigidity is advantater shanks are mounted slightly' out-of-parallel with the axis of rotation of the tool. As a result of this arrangement the shape of the'` cutter may be further simpliiied by taking advantage ofthe fact that Workpieces of' different hardness callI for different slopes or rakes at the cutting' edge. When the tool is to be used exclusively to cut soft materials, which call for a greaterrake' angle, the head is made to support the Shanks in a for-v wardly inclined position so as tof minimize the amount 'of slope or rake that has *to* be ground into the cutter. Where hard materials are to be cut, calling for a lesser rake angle, the tool head is arranged to support the cutter Shanks in a rearwardly inclined position providing a more substantial mounting, and thev amount of rake that has to be ground into the cutter is still not very great.

Other features and advantages will hereinafter appear.

In the accompanying drawing: A Y Figure 1 is a side elevationl of a rotary cutting tool made according to the invention, Y

Fig. 2v is anend elevation of the tool of Fig. 1, looking at the cutting end. y

Fig. 3 is an elevationv of the base end Aof the cutter head, partly in section along lines 3--3 of Fig. l. v y

Fig. 4 is a fragmentary section on the line 4 of Fig. l. K I

Fig. 5 is a side elevation of a cutter of the tool.

Fig. 6 is an end view'of the cutter, taken from l the cutting end.

Fig. '7 is a front edger elevation of the cutter,

and

Fig. 8 is a side* elevation of a modified form of the tool of the present invention.V i

Referring to Figs. 1, 2 andy 3, illustrating a rotary cuttingytool exemplifying the invention,- a driving spindle I0 carries a cutter head' I I having cutters I2, I3 and I4, and a pilot drill I5, the latter being held vby a set screw I5a. The head II has a central bore to receive the spindle I0, and may be keyed to the latter to be driven thereby in any suitable manner, that shown comprising a plurality of shear pins I6 extending from the head to a nange I'I of the spindle.

To hold the head II on the spindle I0' a set screvvY I8 is provided, the tipA of which bears' against the latter.

For the purpose of conveniently mounting' the cutters I2, I3'aifd I4, the head `II is surfaced at three points I9, 2|! and' 2I around its sides, each' surface being at an angle of from the other two, and being parallel to the axis of the spindle I9, Thesurfaces' I9, 20 andZ'I' are provided With grooves Z2,v 23 and 24 respectively in which are carried the cutters I2, I3 and I4', the latter being each held by- YWashers 25 on screws 26 threaded into the head I I. As thus mounted the cutters are adjustable', and may be' advanced to compensate fo'rfvvear, sharpening, etc. f

l According to the* present invention vthere are provided improved' simplified means for backing'v and Supporting the Cutters l2, I3 and I4 td spindle I0.

the cutter I2, the tendencyr to which naturally' As shown in Figs. 1 through 7, the Cutters t2, I3 and I4 have shanks 21, 28 and 29 respectively,

with respective bases 3l), 3| and 32, the latter fitting closely in the grooves 22, 23 land 24, and being of rectangular cross-section which'may be of a stock size, since no parts of the" cutters exl The cutter shank 21 ha's a lead.-`

ceed this size. ing surface 33, a trailing surface 34 and an in'- side surface 35, the latter two surfaces forming the back of the cutter.

In making the cutter I2 for example Figs. 5, 6 and '1, a bar of suitable length is prepared, having a rectangular cross section equal to that of the base 33. The leading surface 33 of the shank 21 is ground in at an angle with respect to the trailing surface 34, so that said surfaces are non" parallelfand I have found that an angle of 5 is satisfactory in this connection. When the cutter I2 is mounted for use on the head I I, the leading surface 33 of the cutter, at the cutting tip, is located so that it lies in the radial line AB (Fig. 2) from the axis of the spindle i3. In order to do this, the leading side of the groove 22 may not coincide with a radialline CD perpendicular to the facing I9 of the head, but must be spaced an extent back of this line. The head I I is pro-vided with backing members 36, 31 and 38 for the cutters I2, I3 and I4 respectively, the backing members Abeing in the form of curved fins broad at their bases and narrowed at their ends. By loeating the cutter I2 on the head II in the manner described, the backing member. 36 may be arranged so that the leading edge-surface thereof will engage the trailing inside corner 33 of the cutter shank 21. This edge-'surface of the backing member may be formed ofvtwo intersecting planar surfaces 40 and 4I, which will coincide with the surfaces 34 and 35 .respectively of the cutter shank 21, and therefore nest the corner 39 of the latter.

As thus arranged, the backing member 35 strongly supports the cutter I2 and prevents same from yielding backward under the stress of the cutting. Also, the surface 4I of the member prevents transverse movement of the cutter I2, inwardly of thehead and the surface 4S prevents transverse movement thereof outwardly of the head. Due to the apparent sharp angle the surface 4I makes with the tangent, designated by the letters EF (Fig. 2), to the line of cutting ,of the cutter I2, it is obvious that the latter is prevented by the backing member 36 from moving radially inward. However, a closer investigation of the functioning of the surface 40 of the backing member in preventing outward radial movement of the cutter I2 seems desirable at this point. As before'noted, the trailing surface 34 of the cutter and the leading surface 33 are not parallel, being inclined at an angle of 5. Thev latter surface is perpendicular to the tangent EF of the line of cutting, and also contains the line AB which extends radially from the axis of the Thus outwardradial movement of tended to intersect the line or plane GH (Fig. 2)

including the contacting surfaces 40 and 34 of Y the'backing member and cutter respectively, the angle of intersection L, measured on the leading 'side of the line GH would be greater than a right fangle, and the less the Value of the retention angle R .of the cutter shank 21, the closer the angle of intersection L approaches a right angle. If the tangent EF to the line of cutting is extended to intersect the line or plane IJ including the contacting surfaces 4I and 35 of the backing member and cutter respectively, the angle M at the intersection would be less than a right angle.l

In a similar manner the backing members 31 and 38 nest the trailing inside corners of the cutter shanks 28 and 29 respectively, and reinforceiand support the cutters I3 and I4 to pren vent chatter and lateral or radial movement thereof. It will be seen also that the cutters I2, I3 and- I4 are readily removable for replacement, and may be adjusted or advanced to compensate for Wear and for sharpening.

As shown in Fig. 6 the cutter I2 has its outside face 42 ground to a section of a cylindrical surface to provide clearance for the Work, the foremost portion 35a of the inside surface 35 being also ground for the same purpose. For the purpose of minimizing drag during cutting, I prefer to grind the surfaces 42 and 35a so that the thickness ofthe shank 21 between these surfaces is slightly less at its center than at the cutting tip, and a total difference of .002 in the thicknesses atthese-two points has proved to be satisfactory. This difference is divided equally so that each of the' surfaces 42 'and 35a is ground to account for.00l less` thickness of the shank 21 at its center. s

VThe cutters I3 and I4 Vare made in a manner similarl to that described for the cutter I2, except for the cutting tips. In order that each cf the cuttersshares'the' cutting load, the tip of the `cutter I2 is ground so that it cuts a V-groove which defines the outermost limits of the total cut, the cutter I4 ground to cut a V-groove which defines the innermost limits of the total cut, and the intermediate cutter I3 ground to 'cut a V- groove intermediate the innermost and outermost'limits. The tip of the cutter I2 is advanced beyond that of the cutter I3 sothat it initiates the cut,'and the tip of the cutter I3 advanced beyond that of the cutter I4. Preferably, the pilot drill I5'is set so 4that the outer edges of the cutting lips are advanced approximately at, ahead of the cutting tip of the cutter I2.

The leading surfaces of the cutters I2, I3 and I4 are ground at the cutting tips to provide true rakes or slopes, as the rake 43 (Fig. 5) of the cutter I2, extending in the path of the chip flow. For hard materials the value ofthe angle N of rake is normally smaller than the value used for soft materials. I have found it to be advantageous, in'connectionwith the construction of cutters and 'backing members described herein as S exemplifying the present invention, to control lthe rake angle of the cutters in part-by giving the latter an angular setting wherein the shanks thereof extend in a direction tangent to either a left hand or right hand helix of small angle, centered in the axis of the spindle IG. By doing this, a tool maybe made up to cut soft material only, and the cutters, by being set with the Shanks extending along a right-hand helix, need be given less of a rake angle Athan if they were set straight, parallel to the axis of rotation. Or if the tool is to be used exclusively for cutting hard materials, a Istronger anchorage for each ofthe cutters-Would result from setting the shanks to extend along a left-hand helix, and due to the material calling for a comparatively small rake angle, the actual angle that is grounded in the cutter, While larger than if the cutter were set straight, is still not excessive. y

Referring to Fig. 1, the cutters I2, I3 and I4 are set so that'the Shanks extend along a lefte hand helix, and I have found that a helix angle P of 1 is satisfactory when the tool is to be used to cut hard materials, including hardened steel. In Fig. 8 the cutters are set in the head IIa so that the Shanks extend along a 'right-hand helix, and When arranged thusly, again with ahelix angle of 1 the tool cuts soft materials suchas soft steel, aluminum, etc. very satisfactorily.

To insure positive positioning of the cutters I2, I3 and I4 a plurality of pins 44,v 45 and 46 are carried by the head I I to engage the cutter bases 30, 3l and 32 respectively. The positions of the cutters may be adjusted by means of shims inserted between the pins and bases, or by grinding off the latter, as required.

The cutting tool of the present invention may be used with or Without the pilot drill I5. If ythe Work to be cutis not too tough, and is mounted rigidly with respect to the mounting for the spindle I0, the drill may be dispensed with. Or a pilot hole may be drilled in the work first, and the drill I5 replaced With a length of drill rod for a pilot. Preferably the drill I5 has flutes, the cutting margins of which are not raised, so that the outer surfaces of the flutes conform to a true right cylinder.

The term nest or nesting as used herein means the interfitting of portions of the cutter blade and backing member so as to provide angular contacting portions extending transversely of the radius passing through said surfaces. As

for example, the surfaces 34, on the back of the cutter blade engage the backing surfaces 4B, 4I along the line or plane GH and IJ both of which are angularly disposed to the radius of the device and hold the cutter blade again-st radial movement when the line GH forms an angle of more than 90 with tangent EF to the line of cutting measured on the leading side of the planc.

Variations and modifications may be made Within the scope of this invention and portions of the improvements may be used Without others.

Iclaim:

ll. A rotary cutter having a head adapted to be fastened to a driving spindle to be rotated thereby; anda cutting member projecting beyond the end thereof and having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head` having a backing member projecting beyond the end thereof and engaging the back kof the cutting member, one of said mem-bers nesting the other so that radial move-` etY ment' of the cutting member is restrained when the tool is cutting.

e 2. A rotatable cutting tool havinga `head adapted to be fastened to a drivingspindle to be rotated thereby; and a cutter having an elongate shank eccentrically mounted on the head to extend in a direc-tion substantially parallel to the axis of rotation thereof, said cutter projecting beyond the end of the head and having a backing member projecting from the end thereof with a leading edge engaging the back of the cutter and lformed to nest the latter and restrain radial movement thereof when the tool is cutting.

3,7A rotatable cutting tool having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank eccentrically mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head having a backing member with a leading portion engaging the back of the cutter and formed to nest the latter and restrain radial movement thereof When the tool is cutting, the nest of the backing member being formed by two surfaces which intersect in a straight line noncoincident with and substantially parallel to the axis of rotation of the head, one of said surfaces being planar and lying outside of the space enclosed by the surface of revolution defined by said intersection during rotation of the head, the plane of said planar surface intersecting a tangent to the line of cutting of the cutter at an angle, measured on the leading side of the is greater than a right angle. Y

4. A rotatable cutting tool having a head adapted to be fastened to aV driving spindle to be rotated thereby; and a cutter having an elongate shank eccentrically mounted on the head to extend in a direction vsubstantially parallel to the axis of rotation thereof, said head having a backing member with a leading portion engaging the back of the cutter and formed to nest the latter and restrain radial movement thereof when the tool is cutting, the nest of the backing member being formed by two surfaces which intersect in a straight line noncoincident with and substantially parallel to the axis of rotation of the head, one of said surfaces being planar and lying inside of the space enclosed by the surface of revolution definedby said intersection during rotation of the head, the plane of said planar surface intersecting a tangent to the line of cutting of the cutter at an angle, measured on the leading side of the plane, which is less than a right angle.

5. A rotatable cutting tool having a head adapted to be fastened to a driving spindle to be rotated thereby; e and a cutter having an elongate shank mounted on the head to extend along a tangent to a right-hand helix about the axis of rotation of the head, the latter having a backing member with a leading edge engaging, and formed so that it nests, the back of the cutter to restrain radial movement thereof when the tool is cutting.

6'. A rotatable cutting tool having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank mounted on the head to extend along a tangent to a left-hand helix about the axis of rotation ofthe head, the latter having a backing member with a leading edge engaging. and formed so that it nests, the back of the out..

plane, which 7 ter to restrain radial movement thereofl when the tool is cutting.

7. The invention as deiined in claim y2, in which the cutter comprises a bar of polygonal section having planar non-parallel leading and trailing surfaces, the latter surface lying in the same plane with, and engaging part of the nesting surface of the Abacking member, and the leading cutter surface Ibeing radial to the line of cutting of the cutter.

8. The invention as dened in claim 2, in which the cutter comprises a bar of polygonal section having planar trailing and inside surfaces Which engage the nest of the backing member.

9. vA rotatable cutting tool having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of Yrotation thereof, said head having a backing member with a portion engaging the cutter, said portion having a surface disposed at less than a right angle with respect to a plane parallel to said axis and containing the tangent to the cutting line of the cutter and another surface disposed at more than a right angle, measured on the leading side of said plane, with respect to said plane.

10. A rotatable cutting tool body having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head having a backing member provided with a V-shaped groove engaging coacting surfaces on the back of the cutter to nest the same therein and press against the same With the apex of the V disposed Within the cutting zone of the cutter.

l1. A rotatable cutting tool body having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head having a backing member having an apexedrgroove engaging coacting surfaces on the back of the'cutter to nest the same therein and press against the same IWith the apex ofthe groove disposed Within the cutting zone of the cutter.

12. A rotatable cutting tool body having a head adapted to be fastened to a driving spindle to be rotated thereby; and a cutter having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head having a backing member provided With a portion engaging the Iback of the cutter to nest the same therein and press against the same, the cutter-engaging face of said portion of the backing member having opposed angularly related surfaces disposed in the cutting zone of the cutter and holding the cutter against shifting laterally with respect to the head.

13. A trepanning tool body having a head adapted to be fastened to a driving spindle to be rotated thereby; Aand one or more cutters carried by the head to project from one end thereof having an elongate shank mounted on the head to extend in a direction substantially parallel to the axis of rotation thereof, said head having a projecting backing member for each cutter engaging the back of the cutter to nest the same therein and pressv against the same, the cutter-engaging portion of the backing member having opposed angularly related surfaces disposed within the cutting zone of the cutter and holding the cutter against shifting laterally with respect to the head.

ANDREW S. FODOR. 

